Fat loss and lean muscle gain in one workout? In just 20-30 minutes? It sounds too good to be true but High Intensity Interval Training (HIIT) can be one of your strongest weapons when looking to improve body composition.

A study in the Journal of Obesity showed 12 weeks of HIIT reduced body fat and increased muscle mass. There were also substantial reductions in abdominal fat and visceral fat, and increases in lean muscle tissue and overall fitness.

But what about steady state cardio (SSC) or low intensity aerobics? Steady state cardio makes the body work in the most efficient way possible – think of a fuel efficient car, it uses as little gas as possible to get from A to B, which is what SSC does for our bodies, so we burn very little fat and carbohydrates when training this way. Going overboard on SSC can also lead to the loss of lean muscle mass (remember we want lean muscle mass as it is a metabolically active tissue that helps us burn calories), increase cortisol production (cortisol is the stress hormone that can lead to belly fat) and hinder increases in both muscle strength and size.

A lot has been written about HIIT, and there are many ways to utilize this training method. Put simply, there are three different energy systems that we can utilize when performing HIIT training.

In terms of efficiency and results the one that provides the most ‘bang for your buck’ when your goal is fat loss (whilst retaining calorie burning lean muscle tissue) is the Anaerobic “Lactic Acid Glycolytic System, which we shall explore in further detail below.

What are the Benefits of Interval Training? 

• It has 3 main physiological benefits: you burn calories during the workout, it prevents lean muscle loss (and can even build lean muscle depending on the type of workout you do), and ensures you burn more calories throughout the day through a process called EPOC (Excess Post-Exercise Oxygen Consumption).

• Its easy to fit in – workouts should be no longer than 20-25 minutes (if you can train any longer than this then you are not working at a high enough intensity and are therefore not reaping the benefits).

• You don’t need any equipment to train this way on your own. Sprints, hill sprints and bodyweight exercises are all great tools for this style of workout.

The Workouts: 

• To start, try a work to rest ratio of 8 seconds on, 12 seconds off. This can be done in many ways, sprints, hill sprints, on a stationary bike, on a rower, etc. Work towards completing 60 rounds, which should take you 20 minutes. This is great for someone who is new to HIIT, and you can work up to the 60 rounds by adding in longer rest periods every 4 -6 rounds. Hill sprints are a great option for beginner as they force you to have good sprint technique (a strong elbow and knee drive), and ensure you are working a the correct intensity.

• To progress, you can lengthen your work time to 30 seconds with a 1 minute recovery between sets.

• If wanting to combine resistance training with HIIT (talk about multi tasking) circuit training with 10 reps per set with 10 seconds rest per exercise for a total of 25 to 30 minutes is a great option. Choose compound exercises such as squats, deadlifts and pull-ups.

• What about Tabata? The 20 seconds on, 10 seconds off protocol, commonly known as Tabata is a another option. However the fact that 1, 4 minute round will produce results is a fallacy (wishful thinking)! Tabata intervals are a great tool, however you will need to complete 4 rounds of the 4 minute protocol to achieve results, or combine it with another HIIT protocol to achieve a total workout time of around 16-20 minutes.

Things to consider:

• Always include a 5 min warm up of pulse raising, multi joint exercises such as High Knees, Star Jumps or Burpees. Think of the R.A.M.P. process: Raise, Activate, Mobilize, Potentiate. Because of the level of intensity needed to reap the benefits of HIIT, a warm up is essential to prime the body for this level of work and to prevent joint and soft tissue injury.

• The work to rest ratio should be between 1:8 to 1:12 when starting interval training in this way, as you become more used to it and the body starts to adapt you can move to a work to rest ratio of 1:6 to 1:10.

• The ‘work’ phase of the workout needs to be ‘all-out’ for the benefits to kick in. If you feel nauseous with your heart jumping out of your chest and your lungs in your mouth you are doing it right! As you progress and your fitness level raises this will become more comfortable, so stay with it!

• If resistance training on the same day as HIIT always resistance train in the morning and HIIT later in the day as you will attain more strength gains when your central nervous system is fresh at the beginning of the day.

• Never repeat the exact same workout twice – just as with resistance training you always want to improve something in each session, either by adding work volume, lengthening the work to rest ratio, or by increasing intensity. This will also keep the workout fresh and interesting, improving compliance.

• Don’t train this way more than 3 times a week, it is challenging on many of the bodies systems and more than 3 times a week can lead to burn-out, especially if training with other modalities (eg. resistance training) in the same training phase.